PLATE TPLATE TECTONICSECTONICS

Chapter 10 Section 1 NotesChapter 10 Section 1 NotesContinental DriftContinental Drift

Alfred Wegener -- 1912, German Alfred Wegener -- 1912, German scientist.scientist.

Proposed a hypothesis called Proposed a hypothesis called “continental drift.”“continental drift.”

The continents once formed part of a The continents once formed part of a single landmass called a single landmass called a “supercontinent” which began to “supercontinent” which began to break up into smaller continents. break up into smaller continents. (about 250 mya)(about 250 mya)

Evidence for “Continental Evidence for “Continental Drift”Drift”

Fossils: if continents were once joined, Fossils: if continents were once joined, fossils of same plants & animals should fossils of same plants & animals should be found in areas once connectedbe found in areas once connected

Rock Formations: ages & types of rocks Rock Formations: ages & types of rocks in coastal regions, matched closely; in coastal regions, matched closely; mountain chains seemed to continue mountain chains seemed to continue across oceansacross oceans

Climate: geologists discovered layers of Climate: geologists discovered layers of debris from glaciers in S. Africa & S. debris from glaciers in S. Africa & S. America.. Too warm today to have America.. Too warm today to have glaciersglaciers

Wegener couldn’t figure out the Wegener couldn’t figure out the “how” part“how” part

1950’s hypothesis by Harry Hess- 1950’s hypothesis by Harry Hess- “Sea-Floor Spreading”.. This was the “Sea-Floor Spreading”.. This was the missing link for Wegener’s hypothesis. missing link for Wegener’s hypothesis.

1960’s – “Paleomagnetism” .. Study of 1960’s – “Paleomagnetism” .. Study of magnetic properties of rocks.magnetic properties of rocks.

By the end of the 1960’s…all the data By the end of the 1960’s…all the data and hypothesis’s were merged to and hypothesis’s were merged to develop the theory of “Plate develop the theory of “Plate Tectonics.”Tectonics.”

Chapter 10 Section 2 NotesChapter 10 Section 2 NotesThe Theory of Plate TectonicsThe Theory of Plate Tectonics

Plate Tectonics: How and why Plate Tectonics: How and why continents move and the study of the continents move and the study of the formation of features in the Earth’s formation of features in the Earth’s crust.crust.

How Continents Move…How Continents Move… Lithosphere- crust Lithosphere- crust

and rigid upper and rigid upper part of the mantle.part of the mantle.

Asthenosphere- Asthenosphere- ‘plastic’ layer ‘plastic’ layer below the below the lithosphere. Flows lithosphere. Flows like putty!like putty!

Two Types of CrustTwo Types of Crust Continental CrustContinental Crust

– Made primarily from silica. Made primarily from silica. – Less dense than oceanic crust.Less dense than oceanic crust.

Oceanic CrustOceanic Crust– Made primarily from iron and magnesium.Made primarily from iron and magnesium.– More dense than continental crust.More dense than continental crust.

What do these densities mean?What do these densities mean?

The Major PlatesThe Major Plates

1.1. North AmericanNorth American2.2. South AmericanSouth American3.3. NazcaNazca4.4. PacificPacific5.5. AntarticAntartic6.6. AfricanAfrican7.7. EurasianEurasian8.8. Indo-AustralianIndo-Australian

TYPES OF PLATE TYPES OF PLATE BOUNDARIESBOUNDARIES

1.1. DIVERGENTDIVERGENT

2.2. CONVERGENTCONVERGENT

3.3. TRANSFORMTRANSFORM

Divergent Plate BoundariesDivergent Plate Boundaries

What does it mean to What does it mean to diverge?diverge?– Plates move apart Plates move apart

2 Types:2 Types:

a)a) Ocean – OceanOcean – Ocean

b)b) Continent – Continent Continent – Continent

Predict what would happen as a result ofa) Ocean-ocean

divergent motion

b) Continent-continent divergent motion

Ocean – Ocean Divergent Ocean – Ocean Divergent BoundariesBoundaries

Sea floor spreading Sea floor spreading creates a Mid-creates a Mid-Oceanic Ridge.Oceanic Ridge.– BasaltBasalt– Undersea volcanoesUndersea volcanoes

Continent – Continent Divergent Continent – Continent Divergent BoundariesBoundaries

Hot magma rises Hot magma rises and causes the and causes the crust to split.crust to split.

Causes the land to Causes the land to drop and form a drop and form a deep valley.deep valley.– Rift valleyRift valley

As spreading As spreading continues, the rift continues, the rift valley will valley will lengthen, deepen, lengthen, deepen, and make a sea.and make a sea.– Red SeaRed Sea

Africa’s Rift Africa’s Rift Valley & Valley & The Red The Red

SeaSea

Convergent Plate Convergent Plate BoundariesBoundaries

What does it mean to What does it mean to converge?converge?

– Plates are moving Plates are moving together. together.

3 Types:3 Types:

1.1. Ocean – OceanOcean – Ocean

2.2. Continent – Continent – ContinentContinent

3.3. Ocean - Continent Ocean - Continent

Based on the model Based on the model belowbelow– Make some Make some

observations about observations about what happens at what happens at convergent plate convergent plate boundariesboundaries

– Predict what would Predict what would happen at these happen at these boundariesboundaries

Oce

an –

Oce

an

Oce

an –

Oce

an

Converg

ent

Boundari

es

Converg

ent

Boundari

es

One oceanic crust dips below One oceanic crust dips below the other – subduction. the other – subduction.

Forms an ocean trench. Forms an ocean trench. Examples include volcanic Examples include volcanic

island arcs such as Japan and island arcs such as Japan and the Caribbean.the Caribbean.

Ocean – Continent Ocean – Continent Convergent BoundariesConvergent Boundaries

Denser oceanic crust Denser oceanic crust subducts below subducts below continental crust.continental crust.

Causes mountains Causes mountains with volcanic activitywith volcanic activity

Examples—Cascade Examples—Cascade Mts. in Washington, Mts. in Washington, Oregon, and Oregon, and California & Andes California & Andes Mountains.Mountains.

Continent – Continent Continent – Continent Convergent BoundriesConvergent Boundries

Continents will smash Continents will smash together, NO together, NO SUBDUCTION, making SUBDUCTION, making mountain ranges.mountain ranges.

Examples include the Examples include the Himalayas.Himalayas.

TRANSFORM BOUNDARIESTRANSFORM BOUNDARIES

Plates are sliding past each other.Plates are sliding past each other. Examples include the San Andres Fault in Examples include the San Andres Fault in

California.California.

Transform BoundariesTransform Boundaries

Occurs when Occurs when two plates slide two plates slide past each past each other.other.

Examples Examples include the San include the San Andres Fault in Andres Fault in California.California.

SAN ANDREAS

ALPINE FAULT BOUNDARY IN NEW ZEALAND

How is plate motion How is plate motion happening?happening?

Scientist’s aren’t really sure!Scientist’s aren’t really sure! They believe ‘convection’ is the main They believe ‘convection’ is the main

reason.reason.

-Convection is the movement of heated -Convection is the movement of heated material due to differences in density material due to differences in density caused by differences in temperature. caused by differences in temperature.

The Earth is a convection system!The Earth is a convection system!Heat (energy) comes from radioactive Heat (energy) comes from radioactive

elements within the Earth’s core. elements within the Earth’s core.

Chapter 10 Section 3 NotesChapter 10 Section 3 NotesThe Changing ContinentsThe Changing Continents

Continents are always changing Continents are always changing shapeshape

Slow movements of tectonic plates Slow movements of tectonic plates change the size & shapechange the size & shape

Rifting = process by which Earth’s Rifting = process by which Earth’s crust breaks apart; can occur within crust breaks apart; can occur within continental or oceanic crustcontinental or oceanic crust

Continental GrowthContinental Growth Continents change not only by breaking Continents change not only by breaking

apart but gaining material tooapart but gaining material too Terrane = a piece of lithosphere that Terrane = a piece of lithosphere that

may be apart of a larger piece of may be apart of a larger piece of lithospherelithosphere

3 characteristics that identifies a terrane3 characteristics that identifies a terrane1.1. Contains rocks & fossils that differ from Contains rocks & fossils that differ from

neighboring terranesneighboring terranes

2.2. Major faults at the boundariesMajor faults at the boundaries

3.3. Magnetic properties don’t match those of Magnetic properties don’t match those of neighboring terranesneighboring terranes

Supercontinent CycleSupercontinent Cycle

Supercontinent cycle = process by Supercontinent cycle = process by which supercontinents form and which supercontinents form and break apart over timebreak apart over time

Supercontinents form because plates Supercontinents form because plates move toward convergent boundaries move toward convergent boundaries & eventually collide..& eventually collide..

Heat then builds under the Heat then builds under the supercontinent & rifts begin to form supercontinent & rifts begin to form & eventually can separate apart.& eventually can separate apart.

PangeaPangea

Pangea formed about 300 myaPangea formed about 300 mya As the continents collided to form As the continents collided to form

Pangea, mountains formed.Pangea, mountains formed. About 250 mya, Pangea began to About 250 mya, Pangea began to

break into 2 continents, Laurasia & break into 2 continents, Laurasia & GondwanalandGondwanaland

These 2 continents eventually These 2 continents eventually separated into our continents that separated into our continents that we have todaywe have today

The FutureThe Future If plates continue to move at current If plates continue to move at current

rate, in about 150 million years, a rate, in about 150 million years, a new supercontinent will formnew supercontinent will form